Unveiling the clinical spectrum of relapsing polychondritis: insights into its pathogenesis, novel monogenic causes, and therapeutic strategies.

Relapsing polychondritis is a rare multisystem disease involving cartilaginous and proteoglycan-rich structures. The diagnosis of this disease is mainly suggested by the presence of flares of inflammation of the cartilage, particularly in the ears, nose or respiratory tract, and more rarely, in the presence of other manifestations. The spectrum of clinical presentations may vary from intermittent episodes of painful and often disfiguring auricular and nasal chondritis to an occasional organ or even life-threatening manifestations such as lower airway collapse. There is a lack of awareness about this disease is mainly due to its rarity. In 2020, VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome, a novel autoinflammatory syndrome, was described. VEXAS syndrome is attributed to somatic mutations in methionine-41 of UBA1, the major E1 enzyme that initiates ubiquitylation. This new disease entity connects seemingly unrelated conditions: systemic inflammatory syndromes (relapsing chondritis, Sweet's syndrome, and neutrophilic dermatosis) and hematologic disorders (myelodysplastic syndrome or multiple myeloma). Therefore, this article reviews the current literature on both disease entities.

Dynamic monitoring of UBA1 somatic mutations in patients with relapsing polychondritis.

BACKGROUND: Commonly clinically diagnosed with relapsing polychondritis (RP), vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome (VEXAS) is a recently identified autoinflammatory disease caused by UBA1 somatic mutations. The low frequency and dynamic changes challenge the accurate detection of somatic mutations. The present study monitored these mutations in Chinese patients with RP. We included 44 patients with RP. Sanger sequencing of UBA1 was performed using genomic DNA from peripheral blood. Droplet digital polymerase chain reaction (ddPCR) was performed to screen low-prevalence somatic variants. RESULTS: Multiple ddPCR detections were performed using available blood samples collected at different follow-up time points. Three male patients were UBA1 somatic mutation carriers. Sanger sequencing detected the somatic UBA1 variant c.122T > C (p.Met41Thr) in two male patients. Initial ddPCR confirmed the variant in the two patients, with allele fractions of 73.75% and 88.46%, respectively, while yielding negative results in other patients. Subsequent ddPCR detected the somatic variant (c.122T > C) with low prevalence (1.02%) in another male patient from blood samples collected at a different time point, and confirmed dynamically fractional abundance in one patient with VEXAS, with allele fractions of 73.75%, 61.28%, 65.01%, and 73.75%. Nine patients assessed by ddPCR at different time points remained negative. CONCLUSION: We report UBA1 variants in patients with RP in the Chinese population for the first time. Multiple ddPCR detections from samples collected at different time points can enhance sensitivity and should be considered for patients with initial negative ddPCR results.

Ultra-rare genetic variation in relapsing polychondritis: a whole-exome sequencing study.

OBJECTIVE: Relapsing polychondritis (RP) is a systemic inflammatory disease of unknown aetiology. The objective of this study was to examine the contribution of rare genetic variations to RP. METHODS: We performed a case-control exome-wide rare variant association analysis that included 66 unrelated European American cases with RP and 2923 healthy controls (HC). Gene-level collapsing analysis was performed using Firth's logistics regression. Exploratory pathway analysis was performed using three different methods: Gene Set Enrichment Analysis, sequence kernel association test and higher criticism test. Plasma DCBLD2 levels were measured in patients with RP and HC using ELISA. RESULTS: In the collapsing analysis, RP was associated with a significantly higher burden of ultra-rare damaging variants in the DCBLD2 gene (7.6% vs 0.1%, unadjusted OR=79.8, p=2.93×10-7). Plasma DCBLD2 protein levels were significantly higher in RP than in HC (median 4.06 ng/µL vs 0.05 ng/µL, p<0.001). The pathway analysis revealed a statistically significant enrichment of genes in the tumour necrosis factor signalling pathway driven by rare damaging variants in RELB, RELA and REL using higher criticism test weighted by eigenvector centrality. CONCLUSIONS: This study identified specific rare variants in the DCBLD2 gene as a putative genetic risk factor for RP. These findings should be validated in additional patients with RP and supported by future functional experiments.

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome (VEXAS syndrome) with prominent supraglottic larynx involvement: a case-based review.

Vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome (VEXAS syndrome) is a recently described genetic disorder that gathers autoinflammatory symptoms and myeloid dysplasia. The first description was reported in 2020, and subsequently, a growing number of cases have been described worldwide. Herein, we describe a case of a 72-year-old male patient with VEXAS syndrome with p.Met41Val mutation of the UBA1 gene, prominent supraglottic larynx involvement, and costochondritis. To our knowledge, this is the first report of VEXAS syndrome in Colombia and South America. This disease could present features of relapsing polychondritis, polyarteritis nodosa, giant cell arteritis, and Sweet syndrome, associated with hematologic involvement, including cytopenias, myelodysplastic syndrome, or thromboembolic disease. Supraglottic larynx chondritis and costochondritis are atypical manifestations. These features were proposed previously to differentiate relapsing polychondritis from VEXAS syndrome but are not entirely reliable like in the case described. A diagnosis of VEXAS should be considered in male patients with incomplete or complete features of the previously described conditions, refractory to treatment, requiring high-dose glucocorticoids, and associated progressive hematologic abnormalities. Key Points • VEXAS syndrome is a recently described genetic (somatic mutations in UBA1 gene) disorder that gathers autoinflammatory and hematologic manifestations. • VEXAS syndrome should be considered in male patients with incomplete or complete features of relapsing polychondritis, polyarteritis nodosa, giant cell arteritis, and Sweet syndrome, refractory to treatment, associated with hematologic involvement, including cytopenias, myelodysplastic syndrome, or thromboembolic disease. • Glucocorticoids ameliorate symptoms effectively. However, other treatment options are limited due to a lack of evidence. Traditional immunosuppressants and biological therapy have been used empirically with limited efficacy and a transient effect. Bone marrow transplant offers a curative approach, but it has high morbidity and mortality.

Co-occurrence of relapsing polychondritis and autoimmune thyroid diseases.

BACKGROUND: Relapsing polychondritis (RP) is a rare inflammatory disease characterized by recurrent inflammation and destruction of cartilaginous tissues. RP has characteristics of autoimmune disease and some reports have noted co-occurrence with autoimmune thyroid disease (AITD), consisting of Graves' disease (GD) and Hashimoto thyroiditis (HT). However, there have been no detailed studies on the co-occurrence of RP and AITD. In this study, we aimed to determine whether patients with RP tend to be complicated with AITD. We also analyzed the clinical and genetic profiles of patients in whom these diseases co-occur. METHODS: We recruited 117 patients with RP and reviewed their medical records. Furthermore, we genotyped Human Leucocyte Antigen (HLA)-A, B Cw, DRB1, DQB1, and DPB1 alleles for 93 of the 117 patients. The prevalence of AITD among the patients with RP was compared with that among the general Japanese population. We also analyzed the clinical and genetic features of the patients with both RP and AITD. RESULTS: The prevalence of GD among the patients with RP was 4.3% (5 among 117 patients), significantly higher than that among Japanese (0.11%) (p = 2.44 × 10-7, binomial test). RP patients with GD tended to have nasal involvement (p = 0.023) (odds ratio (OR) 2.58) and HLA-DPB1*02:02 (p = 0.035, OR 10.41). We did not find significant enrichment of HT in patients with RP. CONCLUSIONS: Patients with RP appear to be at elevated risk of GD. Nasal involvement and HLA-DPB1*02:02 characterize the subset of RP patients with GD, which may guide attempts to characterize a distinct subtype of RP for precision medicine.

A man in his sixties with chondritis and bone marrow failure. / En mann i 60-årene med kondritt og benmargssvikt.

BACKGROUND: VEXAS syndrome (Vacuoles, E1 enzyme, X-linked, Autoinflammatory, Somatic syndrome) first described in 2020, is caused by a limited repertoire of somatic mutations in UBA1, a gene involved in the initiation of ubiquitination. Ubiquitination, adding an ubiquitin protein to a substrate protein, can have various effects on the substrate. Disruption of UBA1 function results in diverse clinical manifestations, mimicking a variety of disorders. CASE PRESENTATION: A man in his sixties presented with fever, chest pain, fatigue, pulmonary infiltrates and elevated acute phase reactants. Initially he was thought to have extra-cranial giant cell arteritis. When he developed ear and nose chondritis, a revised diagnosis of relapsing polychondritis was made. Subsequently he developed macrocytic anaemia and thrombocytopenia. His condition remained resistant to medical therapy and he died eight years after disease onset. Analysis of stored DNA revealed a somatic mutation in UBA1 confirming the diagnosis of VEXAS syndrome. INTERPRETATION: VEXAS syndrome is a newly identified inflammatory disorder due to an acquired mutation in haematopoietic bone marrow cells in older men. The syndrome may be misdiagnosed as treatment-refractory relapsing polychondritis, polyarteritis nodosa, Sweet syndrome or giant cell arteritis. We describe the first individual with molecularly confirmed VEXAS syndrome in Norway.

Pathogenic UBA1 variants associated with VEXAS syndrome in Japanese patients with relapsing polychondritis.

OBJECTIVES: To determine clinical and genetic features of individuals with relapsing polychondritis (RP) likely caused by pathogenic somatic variants in ubiquitin-like modifier activating enzyme 1 (UBA1). METHODS: Fourteen patients with RP who met the Damiani and Levine criteria were recruited (12 men, 2 women; median onset age (IQR) 72.1 years (67.1-78.0)). Sanger sequencing of UBA1 was performed using genomic DNA from peripheral blood leukocytes or bone marrow tissue. Droplet digital PCR (ddPCR) and peptide nucleic acid (PNA)-clamping PCR were used to detect low-prevalence somatic variants. Clinical features of the patients were investigated retrospectively. RESULTS: UBA1 was examined in 13 of the 14 patients; 73% (8/11) of the male patients had somatic UBA1 variants (c.121A>C, c.121A>G or c.122T>C resulting in p.Met41Leu, p.Met41Val or p.Met41Thr, respectively). All the variant-positive patients had systemic symptoms, including a significantly high prevalence of skin lesions. ddPCR detected low prevalence (0.14%) of somatic variant (c.121A>C) in one female patient, which was subsequently confirmed by PNA-clamping PCR. CONCLUSIONS: Genetic screening for pathogenic UBA1 variants should be considered in patients with RP, especially male patients with skin lesions. The somatic variant in UBA1 in the female patient is the first to be reported.

Somatic Mutations in UBA1 Define a Distinct Subset of Relapsing Polychondritis Patients With VEXAS.

OBJECTIVE: Somatic mutations in UBA1 cause a newly defined syndrome known as VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic syndrome). More than 50% of patients currently identified as having VEXAS met diagnostic criteria for relapsing polychondritis (RP), but clinical features that characterize VEXAS within a cohort of patients with RP have not been defined. We undertook this study to define the prevalence of somatic mutations in UBA1 in patients with RP and to create an algorithm to identify patients with genetically confirmed VEXAS among those with RP. METHODS: Exome and targeted sequencing of UBA1 was performed in a prospective observational cohort of patients with RP. Clinical and immunologic characteristics of patients with RP were compared based on the presence or absence of UBA1 mutations. The random forest method was used to derive a clinical algorithm to identify patients with UBA1 mutations. RESULTS: Seven of 92 patients with RP (7.6%) had UBA1 mutations (referred to here as VEXAS-RP). Patients with VEXAS-RP were all male, were on average ≥45 years of age at disease onset, and commonly had fever, ear chondritis, skin involvement, deep vein thrombosis, and pulmonary infiltrates. No patient with VEXAS-RP had chondritis of the airways or costochondritis. Mortality was greater in VEXAS-RP than in RP (23% versus 4%; P = 0.029). Elevated acute-phase reactants and hematologic abnormalities (e.g., macrocytic anemia, thrombocytopenia, lymphopenia, multiple myeloma, myelodysplastic syndrome) were prevalent in VEXAS-RP. A decision tree algorithm based on male sex, a mean corpuscular volume >100 fl, and a platelet count <200 ×103 /µl differentiated VEXAS-RP from RP with 100% sensitivity and 96% specificity. CONCLUSION: Mutations in UBA1 were causal for disease in a subset of patients with RP. This subset of patients was defined by disease onset in the fifth decade of life or later, male sex, ear/nose chondritis, and hematologic abnormalities. Early identification is important in VEXAS given the associated high mortality rate.

Somatic Mutations in UBA1 and Severe Adult-Onset Autoinflammatory Disease.

BACKGROUND: Adult-onset inflammatory syndromes often manifest with overlapping clinical features. Variants in ubiquitin-related genes, previously implicated in autoinflammatory disease, may define new disorders. METHODS: We analyzed peripheral-blood exome sequence data independent of clinical phenotype and inheritance pattern to identify deleterious mutations in ubiquitin-related genes. Sanger sequencing, immunoblotting, immunohistochemical testing, flow cytometry, and transcriptome and cytokine profiling were performed. CRISPR-Cas9-edited zebrafish were used as an in vivo model to assess gene function. RESULTS: We identified 25 men with somatic mutations affecting methionine-41 (p.Met41) in UBA1, the major E1 enzyme that initiates ubiquitylation. (The gene UBA1 lies on the X chromosome.) In such patients, an often fatal, treatment-refractory inflammatory syndrome develops in late adulthood, with fevers, cytopenias, characteristic vacuoles in myeloid and erythroid precursor cells, dysplastic bone marrow, neutrophilic cutaneous and pulmonary inflammation, chondritis, and vasculitis. Most of these 25 patients met clinical criteria for an inflammatory syndrome (relapsing polychondritis, Sweet's syndrome, polyarteritis nodosa, or giant-cell arteritis) or a hematologic condition (myelodysplastic syndrome or multiple myeloma) or both. Mutations were found in more than half the hematopoietic stem cells, including peripheral-blood myeloid cells but not lymphocytes or fibroblasts. Mutations affecting p.Met41 resulted in loss of the canonical cytoplasmic isoform of UBA1 and in expression of a novel, catalytically impaired isoform initiated at p.Met67. Mutant peripheral-blood cells showed decreased ubiquitylation and activated innate immune pathways. Knockout of the cytoplasmic UBA1 isoform homologue in zebrafish caused systemic inflammation. CONCLUSIONS: Using a genotype-driven approach, we identified a disorder that connects seemingly unrelated adult-onset inflammatory syndromes. We named this disorder the VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic) syndrome. (Funded by the NIH Intramural Research Programs and the EU Horizon 2020 Research and Innovation Program.).

Genetic basis of relapsing polychondritis revealed by family-based whole-exome sequencing.

AIM: Genetic factors are believed to be implicated in the pathogenesis of relapsing polychondritis (RP). However, the molecular genetic determinants remain to be elucidated. This study aimed to detect the susceptibility genes of RP with whole-exome sequencing (WES) in a Chinese family and deepen our understanding of the pathogenesis of RP thereafter. METHOD: A 32-year-old Chinese female proband with RP and her family including her mother with RP were enrolled in the study. The genomic DNA of 6 human subjects was extracted from peripheral blood and then gene allele mutations were identified using WES. Candidate variants with low frequency (<0.1%) in the general population and predicted deleterious effects on gene function were identified. Sanger sequencing was applied subsequently to confirm the analyzed gene variants in 12 human blood samples. RESULTS: Nine single nucleotide polymorphism variants from different genes were identified to associate with RP by WES and further confirmed by Sanger sequencing, including Ring finger protein 207 (RNF207), collagen type XXII alpha 1 chain (COL22A1) rs200464636, glycosylphosphatidylinositol anchor attachment 1 (GPAA1) rs201424010, recQ like helicase 4 (RECQL4) rs757703895, folliculin (FLCN) NM_144606: c.G838A: p.E280K, DNA ligase 3 (LIG3) rs761808558, NM_207396: c.T425C:p.I142T, myosin heavy chain 15 (MYH15) NM_014981: c.G4462A: p.A1488T, purkinje cell protein 2 (PCP2) rs144974437 and coiled-coil domain containing 61 (CCDC61) rs777816675. CONCLUSIONS: This study suggests that coinheritance of multigene mutation may contribute to RP predisposition. The candidate genes mutated which we discovered are potential targets for in-depth functional studies.

P63-related disorders: Dermatological characteristics in 22 patients.

In P63-related ectodermal dysplasias (ED), the clinical characteristics focus on extra-cutaneous manifestations. The dermatological phenotype remains incompletely characterized. We report the dermatological features of 22 patients carrying a TP63 mutation. Erosions, erythroderma and pigmentary anomalies are characteristics of P63-related ED. Our data suggest that patients might be classified into two major P63-related disorders: AEC and EEC. RHS and ADULT represent mild AEC and EEC forms, respectively.

An Ashkenazi Jewish founder mutation in CACNA1F causes retinal phenotype in both hemizygous males and heterozygous female carriers.

Background: Mutations in CACNA1F have been mainly associated with X-linked incomplete congenital stationary night blindness (icCSNB). Variable phenotypic expression in females was reported in some families. We report here three non-related Ashkenazi Jewish families originating in Eastern Europe, that included males and a many affected females, initially diagnosed with variable retinal phenotypes.Materials and Methods: Whole exome sequencing (WES), Sanger sequencing and microsatellite haplotyping were used for genetic analysis. Complete ophthalmologic examination was performed including visual acuity, refraction, colour vision, slit-lamp, fundoscopy and electroretinography (ERG).Results: We identified four affected males, showing moderate visual impairment, and seven female carriers, six of them presenting mild to moderate visual impairment. Infantile nystagmus was found in all affected males and in 5/7 females. Nyctalopia and myopia were common in both males and females. Initial clinical differential diagnosis included cone-dystrophy, cone-rod dystrophy, cone-dystrophy with supernormal rod response or CSNB based on ERG results. WES and Sanger sequencing revealed a previously described missense mutation c.2225T>G; p.(F742C) in CACNA1F (NM_001256789.2) in all three families, encompassed by a shared haplotypeConclusions: Our data suggests that p.(F742C) in CACNA1F is an X-linked founder mutation in Ashkenazi Jews originating in Eastern Europe. This mutation causes a mild-to-moderate icCSNB phenotype, expressed in most female carriers. A targeted test for this variant in suspected patients may initiate diagnostic analysis. Our results highlight the relevance of WES in the clinic, allowing fast and accurate diagnosis for unclear and variable clinical phenotype and in pedigrees with multiple possible inheritance patterns.

Evaluation of computational genotyping of structural variation for clinical diagnoses.

BACKGROUND: Structural variation (SV) plays a pivotal role in genetic disease. The discovery of SVs based on short DNA sequence reads from next-generation DNA sequence methods is error-prone, with low sensitivity and high false discovery rates. These shortcomings can be partially overcome with extensive orthogonal validation methods or use of long reads, but the current cost precludes their application for routine clinical diagnostics. In contrast, SV genotyping of known sites of SV occurrence is relatively robust and therefore offers a cost-effective clinical diagnostic tool with potentially few false-positive and false-negative results, even when applied to short-read DNA sequence data. RESULTS: We assess 5 state-of-the-art SV genotyping software methods, applied to short-read sequence data. The methods are characterized on the basis of their ability to genotype different SV types, spanning different size ranges. Furthermore, we analyze their ability to parse different VCF file subformats and assess their reliance on specific metadata. We compare the SV genotyping methods across a range of simulated and real data including SVs that were not found with Illumina data alone. We assess sensitivity and the ability to filter initial false discovery calls. We determined the impact of SV type and size on the performance for each SV genotyper. Overall, STIX performed the best on both simulated and GiaB based SV calls, demonstrating a good balance between sensitivity and specificty. CONCLUSION: Our results indicate that, although SV genotyping software methods have superior performance to SV callers, there are limitations that suggest the need for further innovation.

Relapsing polychondritis: a chameleon among orphan diseases.

Relapsing polychondritis (RPC) is a rare disease with recurrent episodes of inflammation of cartilage tissue leading to fibrosis and organ damage. Despite unknown etiology, there is some evidence of a genetic predisposition. The clinical presentation is heterogeneous and an association with other autoimmune disorders such as rheumatoid arthritis or different forms of vasculitis has been described. All organ systems containing cartilage can be affected, such as ear, nose, joints, trachea, aorta, and coronary arteries. Given the broad spectrum of potential manifestations, a variety of medical specialists may be involved in the management of RPC patients. As establishing the diagnosis of RPC may be difficult, an interdisciplinary approach may be preferable. Treatment options include glucocorticoids, dapsone, disease-modifying antirheumatic drugs, and biologics. Prognosis is as heterogeneous as the clinical picture, depending on the severity of organ damage. In this paper we give an overview of the current knowledge with regard to pathogenesis, clinical picture, diagnosis, and therapy of RPC.

Genotyping of relapsing polychondritis identified novel susceptibility HLA alleles and distinct genetic characteristics from other rheumatic diseases.

OBJECTIVE: To uncover the genetic background of relapsing polychondritis (RPC), a rare autoimmune disease with unknown mechanisms characterized by systemic inflammation of the cartilage, to deepen our understanding of the pathophysiology of RPC and show its distinct genetic characteristics from other rheumatic diseases. METHODS: A total of 102 patients with RPC and 1000 healthy subjects were recruited for a two-staged genetic association study and genotyped for six HLA classical loci. Haplotype association tests were also performed. The associations of amino acid (AA) residues and positions with susceptibility to RPC were analysed. Frequencies of representative susceptibility HLA alleles to other rheumatic diseases in RPC were also analysed. RESULTS: HLA-DRB1*16:02, HLA-DQB1*05:02 and HLA-B*67:01, which are in linkage disequilibrium with each other, were associated with RPC (P = 1.9 × 10(-6), 1.4 × 10(-5) and 0.00024, respectively). AA residue at position 57 in HLA-DQB1, the most significant position in type I diabetes mellitus, showed the strongest association among AA residues. HLA-DR4, a known susceptibility allele in Germans, showed a trend of susceptibility association without significance (P = 0.067). No associations were observed between the three alleles and clinical phenotypes. Representative susceptibility HLA alleles to RA, SLE, Behçet disease and Takayasu arteritis did not show enrichment in RPC in spite of sufficient statistical power. CONCLUSIONS: HLA-DRB1*16:02, HLA-DQB1*05:02 and HLA-B*67:01, in linkage disequilibrium with each other, are associated with susceptibility to RPC Importance of HLA-class II loci in RPC susceptibility is suggested. RPC is considered a genetically distinct disease from other rheumatic diseases.

Keutel syndrome: report of two novel MGP mutations and discussion of clinical overlap with arylsulfatase E deficiency and relapsing polychondritis.

Keutel syndrome is a rare, autosomal recessive disorder characterized by diffuse cartilage calcification, peripheral pulmonary artery stenosis, midface retrusion, and short distal phalanges. To date, 28 patients from 18 families have been reported, and five mutations in the matrix Gla protein gene (MGP) have been identified. The matrix Gla protein (MGP) is a vitamin K-dependent extracellular protein that functions as a calcification inhibitor through incompletely understood mechanisms. We present the clinical manifestations of three affected siblings from a consanguineous Turkish family, in whom we detected the sixth MGP mutation (c.79G>T, which predicts p.E27X) and a fourth unrelated patient in whom we detected the seventh MGP mutation, a partial deletion of exon 4. Both mutations predict complete loss of MGP function. One of the patients presented initially with a working diagnosis of relapsing polychondritis. Clinical features suggestive of Keutel syndrome were also observed in one additional unrelated patient who was later found to have a deletion of arylsulfatase E, consistent with a diagnosis of X-linked recessive chondrodysplasia punctata. Through a discussion of these cases, we highlight the clinical overlap of Keutel syndrome, X-linked chondrodysplasia punctata, and the inflammatory disease relapsing polychondritis.